This invention relates to medical imaging equipment having scanning imaging detectors and, more particularly, to a proximity sensor for controlling the distance between the imaging detector and the subject to be scanned.
In nuclear medicine imaging scans, the imaging detector must often be rotated around or passed over the patient or subject. In the first instance, referred to as SPECT (single photon emission computed tomography), the imaging detector acquires a number of images from various viewing angles around the subject. A computer will later reconstruct from these views a three-dimensional volume representation of the patient's anatomy. A SPECT apparatus is shown in U.S. Pat. No. 5,055,687, which is included herein in its entirety by reference.
In the second instance, referred to as whole body imaging, the detector slowly translates over the subject (or equivalently, the subject is translated past the detector) to generate an image which is much larger than the detector's field of view.
In both of these operations, scanning the detector is necessary as opposed to simple spot viewing of a portion of the subject. In order to maintain the best spatial resolution in the image, the detector must be maintained as close to the subject as practical. Approximately 1 mm of resolution is lost for every additional 1 cm of distance between the detector and the subject.
In order to better follow the contour of the subject, many manufactures of SPECT and whole body scanners permit the operator to "teach" the motion-control hardware or manipulator the trajectory that the detector must take around or over the subject. This is done by manually moving (via hand-operated controls) the detector about the subject. The imaging device memorizes this motion and repeats it during the actually scanning operation.
This teaching operation is performed prior to and in addition to the actual imaging scan of the subject. This is a very time-consuming operation. It increases the labor and machine-time required for a scan, lowers scanner throughput, and requires the subject to be confined to the scanner for a greater time. Particularly in the case of trauma, this delay is undesirable for clinical use.
In addition, the quality of the images obtained is dependent on the technique and skill of individual operators during the teaching process.